The present application claims priority under 35 U.S.C. xc2xa7119 of German Patent Application No. 198 30 896.5, filed on Jul. 10, 1998, the disclosure of which is expressly incorporated by reference herein in its entirety.
1. Field of the Invention
The present invention relates to a photoplotting process for high energy plotting of a computer-stored raster image on a photosensitive record carrier.
2. Discussion of Background Information
Photoplotting processes and arrangements serve, for example, to produce photographic artwork for printed circuit boards.
Photoplotters plotting a computer-stored raster image on a plane, photosensitive record carrier are known from the prior art (information sheet Xenon Plotter by the company MIVATEC Hard- und Software GmbH, Benzstrasse, 17, D71171 Schxc3x6naich, of 15.10.1996).
During said plotting, a so-called exposure head (with a plotting area of about 5xc3x977.5 mm) is guided over a record carrier, which has a large area (up to approximately 720xc3x97600 mm) in relation thereto, for the purpose of plotting picture elements composing the raster image of the record carrier.
The exposure head is provided with an LCD matrix of light-modulation elements (LCD: liquid crystal device), each of which can be selectively controlled by electrical means in order to open or block it for transmitted light.
If transmitted light is projected onto this LCD matrix, it can only pass as a xe2x80x98light beamxe2x80x99 through the matrix at those elements that are controlled to admit the passage of light.
Each of the light beams admitted forms a corresponding picture element on the photosensitive record carrier. Missing light beams-equivalent to blocked elements-form xe2x80x98missing picture elementsxe2x80x99.
The raster image of the record carrier consists of a multiplicity of picture elements, including plotted and non-plotted (missing) picture elements.
In the above arrangement light from a Xenon flash lamp is projected onto the LCD matrix.
Since the exposure head containing the LCD matrix has a much smaller area (comparable to the square of a chessboard) than the record carrier (comparable to a chessboard having many squares), said exposure head must be guided successively to all the positions of the chessboard squares so that the picture elements can be plotted there.
In view of the desired high resolution (in the range of greater than 10 micrometers) of the raster image of the record carrier, the movement of the exposure head imposes the highest tolerance requirements with respect to the precision of the movement mechanism for displacement of the head.
Because the exposure head is moved continuously over the record carrier, there is only a very short moment to illuminate the head (by means of a Xenon flash lamp) aligned at a xe2x80x98chessboard fieldxe2x80x99 of the record carrier. A longer exposure period would lead to blurred picture elements (with xe2x80x98comet trailsxe2x80x99) through sustained movement of the head, effectively influencing the resolution of the plotting disadvantageously.
Short exposure periods are, however, associated with minimal plotting energy, which again signifies that only photographic artwork, such as for subsequent circuit board manufacture, can be prepared. Such a comparatively small quantity of plotting energy obviates direct exposure of so-called circuit board photo-resist material.
The present invention relates to a process having a comparatively higher plotting energy, which also makes use of an exposure head being moved continuously. The plotting energy should be sufficiently high to enable direct exposure of photo-resist material.
A further object of the present invention is to propose a photoplotting process which permits plotting a raster image of the record carrier with variable image scale.
In accordance with the present invention, during relative displacement between the light modulator and the record carrier, the excursion of the light beams emanating from the light modulator and impacting a sub-area of the record carrier raster image are compensated during a time interval T by a displacable lens disposed between the light modulator and record carrier. Time interval T is above a value W1, which relates to the permissible maximum displacement path of the relative movement for the resolution of plotting without use of the lens, and is below a value W2, which relates to a time interval that begins in a current sub-area of the record carrier raster image during the projecting entry of the first half of the light modulator surface and that ends only when the second half of the light modulator surface projects into this sub-area of the record carrier raster image, reduced by the reverse period for the lens. The lens, after recording the picture elements in a record carrier raster image sub-area is displaced in a direction opposite to the compensation direction into a starting position for plotting of the next sub-area of the record carrier raster image.
Accordingly, the instant invention relates to a process for plotting of a raster image on a light-sensitive record carrier. The process includes converting a computer-stored raster image comprising raster points into controllable raster point-related light beams via a light modulator, such that picture elements corresponding to the raster points are plotted on a record carrier, matrix-like dividing of the computer raster image into imaginary computer raster image sub-areas, and matrix-like dividing of the record carrier raster image is into imaginary record carrier raster image sub-areas, wherein the sub-areas of the computer and record carrier raster image are associated with one another. The process further includes matrix-like dividing of the imaginary computer raster image sub-areas into imaginary raster point positions, matrix-like dividing of the imaginary computer raster image sub-areas into n imaginary raster point positions, and matrix-like dividing of the sub-areas of the record carrier raster image into n imaginary picture element positions. Further, the process includes assigning the picture element positions to the raster image positions, simultaneously plotting the picture elements corresponding to the raster points of a sub-area of a record carrier raster image, successively plotting the sub-areas of the record carrier raster image, continuously moving a light modulator relative to the record carrier to capture an entire surface of the record carrier according to the sub-areas of the record carrier raster image, and projecting the light modulator for each sub-area of the record carrier raster image with light. During relative displacement between the light modulator and the record carrier, an excursion of the light beams emanating from the light modulator and impacting a sub-area of the record carrier raster image are compensated during a time interval T by a displaceable lens disposed between the light modulator and record carrier. The time interval T is selected to be above a value W1, which relates to a maximum permissible displacement path for the relative movement for plotting resolution without use of the displaceable lens, and to be below a value W2, which relates to a time interval that begins when a first half of the light modulator surface projects into a specified sub-area of the record carrier raster image and that ends when only a second half of the light modulator surface projects into the specified sub-area of the record carrier raster image, and is reduced by a reverse period for the displaceable lens. The displaceable lens, after recording the picture elements in a record carrier raster image sub-area, is displaced in a direction opposite to the compensation direction into a starting position for plotting of the next sub-area of the record carrier raster image.
In accordance with a feature of the present invention, the light modulator can include a tilting mirror element semiconductor chip.
According to another feature of the present invention, the light modulator can include a liquid crystal arrangement.
According to still another feature of the instant invention, the light modulator may include one of a magneto-optical and ferro-optical electrical arrangement.
In accordance with a further feature of the present invention, the light source may be adapted to emit sustained light. Further, the light source may include a mercury arc lamp.
In accordance with another feature of the present invention, the record carrier material can be in a liquid state prior to plotting.
In accordance with a still further feature of the instant invention, the displaceable lens may include a multiple element lens that determines a focussing scale.
The present invention also relates to a process for a plotting raster image on a light-sensitive carrier. The process includes continuously displacing an exposure head, comprising a light modulator, relative to the light-sensitive record carrier, positioning a lens between the exposure head and the light-sensitive record carrier, and displacing the lens relative to the exposure head and light-sensitive record carrier.
In accordance with a feature of the invention, the process can further include directing a sustained light beam onto the exposure head.
According to another feature of the instant invention, the process may further include directing a sustained light beam from a mercury arc lamp onto the exposure head.
According to still another feature of the present invention, the displacing of the lens relative to the exposure head and the light-sensitive record carrier compensates for blurring.
In accordance with a further feature of the invention, the process further includes logically subdividing the light-sensitive record carrier into a matrix-like arrangement, wherein each entry of the matrix-like arrangement corresponds to a portion of the raster image to be plotted.
According to still another feature of the instant invention, the process can further include, during plotting, adjusting the exposure head so that light, through the lens, is incident upon the light-sensitive: record carrier; after plotting, adjusting the exposure head so that light is not incident upon the light-sensitive carrier, and returning the lens to a starting position.
In accordance with a further feature of the invention, a drive unit can be coupled to the light-sensitive record carrier and the exposure head is fixedly positioned.
In accordance with a still further feature of the present invention, a drive unit can be coupled to the exposure head and the light-sensitive record carrier is fixedly positioned.
According to still another feature of the present invention, during plotting, the lens is displaced in a direction opposite a direction of the relative movement of the exposure head, and, after plotting, the lens is displaced in a same direction as the direction of relative movement of the exposure head.
The instant invention relates to an apparatus for plotting a raster image. The apparatus includes an exposure head comprising a light modulator, a light-sensitive record carrier, and a plotting drive unit coupled to at least one of the exposure head and the light-sensitive record carrier. In this manner, the exposure head and the light-sensitive record carrier are adapted for relative movement to each other. The apparatus also includes a lens positioned between the exposure head and the light-sensitive record carrier, and a lens drive unit coupled to the lens. In this manner, the lens is adapted for movement relative to the exposure head and light-sensitive record carrier.
In accordance with yet another feature of the instant invention, a light source may be adapted to emitting a sustained light beam. The light source may include a mercury arc lamp.
The present invention relates to an apparatus for plotting of a raster image on a light-sensitive record carrier. The apparatus includes a light modulator adapted to convert a computer-stored raster image comprising raster points into controllable raster point-related light beams. Picture elements corresponding to the raster points are plotable on a record carrier. A logic device is provided that matrix-like divides the computer raster image into imaginary computer raster image sub-areas, that matrix-like divides the record carrier raster image is into imaginary record carrier raster image sub-areas, wherein the sub-areas of the computer and record carrier raster image are associated with one another, that matrix-like divides the imaginary computer raster image sub-areas into imaginary raster point positions, a logic device that matrix-like divides the imaginary computer raster image sub-areas into n imaginary raster point positions, and that matrix-like divides the sub-areas of the record carrier raster image into n imaginary picture element positions. The picture element positions are assigned to the raster image positions. A plotting device is included that simultaneously plots the picture elements corresponding to the raster points of a sub-area of a record carrier raster image and that successively plots the sub-areas of the record carrier raster image. The light modulator is continuously movable relative to the record carrier to capture an entire surface of the record carrier according to the sub-areas of the record carrier raster image. A device that projects the light modulator for each sub-area of the record carrier raster image with light is provided, as is a displaceable lens disposed between the light modulator and the record carrier. During relative displacement between the light modulator and the record carrier, an excursion of the light beams emanating from the light modulator and impacting a sub-area of the record carrier raster image during a time interval T are compensated with the displaceable lens. The time interval T is above a value W1, which relates to a maximum permissible displacement path for the relative movement for plotting resolution without use of the displacable lens, is below a value W2, which relates to a time interval that begins when a first half of the light modulator surface projects into a specified sub-area of the record carrier raster image and that ends when only a second half of the light modulator surface projects into the specified sub-area of the record carrier raster image, and is reduced by a reverse period for the displacable lens. A lens displacing device is provided that moves the displaceable lens, after recording the picture elements in a record carrier raster image sub-area, in a direction opposite to the compensation direction into a starting position for plotting of the next sub-area of the record carrier raster image.
Other exemplary embodiments and advantages of the present invention may be ascertained by reviewing the present disclosure and the accompanying drawing.